using System;

public class Program

{

    public static void Main()

    {

        int a = 5;

        int b = 6;

        _swapWontWork(a,b);

        Console.WriteLine("a={0}, b={1}",a,b);

        _swap(ref a, ref b);

        Console.WriteLine("a={0}, b={1}",a,b);

    }

    static void _swapWontWork(int a, int b)

    {

                 int tmp = a;

         a = b;

         b = tmp;

    }

    static void _swap(ref int a, ref int b)

    {

         int tmp = a;

         a = b;

         b = tmp;

    }

}